In the past, containers (e.g., basins or tanks) have been provided to house apparatus in which materials are collected. For example, materials may be collected from liquids by plate or tube settlers that promote settling of the material to the bottom of the basin. In other cases, flocculators may be housed in such containers, and materials often inadvertently move in the flocculators to the bottom of the basin. Because the flocculators are designed to circulate the liquid and materials, rather than to promote settling of the materials, the materials that inadvertently collect at the bottom of the basin present a problem. In both cases, the materials on the bottom may be referred to as sludge.
In the case of the settlers, for example, the sludge is collected, or removed, from the bottom to make room for more sludge as more liquid and materials flow into the basin and the materials settle and become sludge. In the past, sludge collection equipment has been mounted on or near the bottom for gathering the sludge and causing the sludge to flow out of the basins. Such equipment has included a so-called header pipe (e.g., a hollow tube), known as a “header”, and mounted for movement along a path adjacent to the bottom. The header is below the settler plates of a settler, for example. Low pressure has been applied to the header as the header is moved along the path. Holes in the header admit the sludge and liquid from the bottom of the basin. The holes may be of the type described in U.S. Pat. No. 5,914,049, issued on Jun. 22, 1999, and entitled “Method and Apparatus For Helical Flow In Header Conduit”, the disclosure of which is incorporated by reference. Under the action of the low pressure, the sludge and the liquid flow into and through the header, and from the header through a flexible outlet hose to a discharge location out of the basin.
The low pressure has been applied to the header by the flexible outlet hose. Such hoses have generally been small diameter hoses, e.g., not exceeding four inches in diameter. Also, the flexible hoses are typically ribbed on the inside, which restricts the inside diameter and increases head loss. Generally, such small diameter hoses can only induce a maximum flow rate of about 200 gallons per minute (gpm) in the header. Thus, the flow rate through the header has been limited by the flow capacity of the flexible outlet hoses.
An unacceptable solution to this flow rate problem is to use many of the flexible hoses. That solution is unacceptable because the flexible outlet hoses can flex. Each flexible hose is thus free to rise (i.e., float) above the header under buoyancy forces of gases in the flexible outlet hose. As a result, the flexible hoses have in the past risen above the header and a portion of each flexible hose has assumed an inverted U-shape. Unfortunately, because the U-shaped portion is above the level of the header, and is above the level of an outlet of the flexible hose from the basin, the gas becomes trapped in such inverted U-shaped portion, making it difficult to prime the hose when starting the sludge collecting operation. When many flexible hoses are used to provide more flow rate from the header, the priming problem is increased.
Also, because the flexible outlet hoses tend to float, these hoses tend to interfere with the operation of the settlers, which extend downwardly in the basin toward the bottom and provide a low-clearance configuration at the bottom of the basin. A similar problem would exist with attempts to use such hoses to remove the material from beneath the flocculators.
Another unacceptable solution to this flow rate problem is to provide a telescopic conduit arrangement in which a difference in diameter between an inner conduit and an outer conduit is increased to provide, on a sealing means that tightly seals the inner conduit to the outer conduit, an area subject to differential pressure to drive a sludge take-up system across a floor of a basin. Unacceptable aspects of such sealing means include a reduction in sludge flow rate through the telescopic arrangement due to pressure drop caused by the driving of the sludge take-up system. Also, the tight seal of the sealing means increases the force required to slide one conduit relative to the other conduit, and thus increases the force required to drive the sludge take-up system across a floor of a basin. In turn, this requires more pressure drop and resulting reduction in sludge flow rate through the telescopic arrangement. Further, the tight sealing means moves along a path near a longitudinal axis of the telescopic conduit arrangement and does not allow collection of the sludge from near such axis.
What is needed then is a way of allowing collection of the sludge from near the longitudinal axis of the sludge collecting system, while allowing the sludge collecting system to traverse the header from one end of a very long basin to the opposite end of the very long basin, and without decreasing the flow of the sludge from the system, so that sludge will not build-up near such axis, thus avoiding interference with traverse of the header from one end of the basin to the opposite end of the basin, for example.